The invention relates generally to the treatment of masters or originals.
More particularly, the invention relates to the treatment of exposed and developed lengths of photosensitive material having a plurality of exposures. Each of the lengths further has a plurality of uncoded and/or coded exposure identification numbers imaged onto a longitudinal margin. The lengths are conveyed along a predetermined path and are sensed in a measuring station disposed along the path. Sensing of the lengths may, for example, be performed photoelectrically by illuminating the lengths via a scanning slit which extends normal to the path.
Films of small size currently in use have uncoded exposure identification numbers, and sometimes machine-readable, coded exposure identification numbers, imaged onto a longitudinal margin. By means of these numbers, a customer can identify the exposures to be copies, e.g., when ordering additional copied. To facilitate this, the German Auslegeschrift 11 85 472 describes a method in which the exposure identification numbers are read in a copier and then imprinted on the backs of the corresponding copies. The publication also discloses a simplified method for handling orders for additional copies. Here, the film is introduced into the copier and, at the same time, the exposure identification number of the exposure to be copied is inputted. The film is thereupon properly positioned in the copying station automatically and a paper copy produced.
Difficulties can arise both with the imprinting of the exposure identification number on the back of the copy and with the positioning of the film following entry of the exposure identification number. The reason is that the exposure identification number cannot always be clearly linked to the corresponding exposure.
To solve this problem, the European patent application 320 880 provides a sensor to detect the coded or uncoded exposure identification number. The publication proposes to measure the distance travelled by the number during film transport until the exposure is positioned in the copying station. The detected exposure identification number is associated with the exposure when the distance travelled lies within predetermined limits.
Problems can occur with this method also if, for instance, the distances between exposures are not equal to the distances between numbers; if individual exposure identification numbers are destroyed because of damage to the film; or if errors arise during reading of the exposure identification numbers.